Konevega L V, Kalinin V L
Konstantinov Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Russia.
Genetika. 1998 Jul;34(7):897-902.
The lethal and mutagenic effects of the decay of 3H incorporated in phage lambda DNA as 8-3H-adenosine and 8-3H-guanosine were studied, using the DNA of 8-3H-adenine as a labeled DNA precursor. A transmutation component of 3H decay is involved in formation of 8-oxoguanine (8-oxo-G) and 8-oxoadenine (8-oxo-A) residues in phage DNA. The efficiency of phage inactivation (the number of lethal lesions per one tritium decay in the phage genome) for 3H decay in position 8 of purines was the same as that measured in positions 5 and 6 of pyrimidines (alpha = 0.14 +/- 0.01) and virtually did not depend on the fpg-1::kan mutation in the host gene encoding the Fpg protein (formamidepyrimidine-DNA-glycosylase). The efficiency of the mutagenic effect of 3H-purines Em (frequency of c mutations per one 3H decay in the phage genome) was (2.9 +/- 0.3) x 10(-5) in the fpg+ host and (4.6 +/- 0.4) x 10(-5) in the fpg-host. This means that the Fpg protein excised approximately 40% of premutational DNA lesions (probably, 8-oxo-G residues). Induction of the mutagenic SOS system by UV light caused a 1.5-fold increase in the frequency of c mutations induced by 8-3H-purines in fpg+ cells over that in fpg-cells. This suggests that apurinic AP sites produced after the excision of 8-oxo-G by the Fpg protein are substrates for mutagenic SOS repair.
以8 - ³H - 腺嘌呤的DNA作为标记DNA前体，研究了掺入噬菌体λDNA中的³H以8 - ³H - 腺苷和8 - ³H - 鸟苷形式衰变的致死和诱变效应。³H衰变的一种嬗变成分参与了噬菌体DNA中8 - 氧代鸟嘌呤（8 - oxo - G）和8 - 氧代腺嘌呤（8 - oxo - A）残基的形成。嘌呤第8位³H衰变导致的噬菌体失活效率（噬菌体基因组中每一次氚衰变产生的致死损伤数）与嘧啶第5位和第6位测量的效率相同（α = 0.14 ± 0.01），并且实际上不依赖于宿主基因中编码Fpg蛋白（甲酰胺嘧啶 - DNA - 糖基化酶）的fpg - 1::kan突变。³H - 嘌呤诱变效应的效率Em（噬菌体基因组中每一次³H衰变产生的c突变频率）在fpg⁺宿主中为(2.9 ± 0.3)×10⁻⁵，在fpg⁻宿主中为(4.6 ± 0.4)×10⁻⁵。这意味着Fpg蛋白切除了约40%的突变前DNA损伤（可能是8 - oxo - G残基）。紫外线诱导诱变的SOS系统导致fpg⁺细胞中8 - ³H - 嘌呤诱导的c突变频率比fpg⁻细胞中增加了1.5倍。这表明Fpg蛋白切除8 - oxo - G后产生的无嘌呤AP位点是诱变SOS修复的底物。
